(a) Field of the Invention
The present invention relates to a base station, a relay station, and a mobile station. More particularly, the present invention relates to a method and apparatus for sending and receiving Multicast Broadcast Service (MBS) data.
(b) Description of the Related Art
In a mobile communication system using a multi-carrier, data transmitted through one carrier supporting MBS may be divided into a plurality of subbands on the frequency axis. All subbands may be allocated to an MBS region. Furthermore, those subbands may be allocated an MBS region and a non-MBS region for providing service other than MBS, such as unicast service. Each region is allocated at least one subband.
Meanwhile, the MBS region may be divided into multiple MBS zones. Each MBS zone is allocated at least one subband.
Accordingly, an MBS transmitting apparatus, such as a base station or a relay station, is required to send information to an MBS receiving apparatus, such as a mobile station, so that the MBS receiving apparatus can recognize an MBS region and identify each MBS zone based on the information.
Therefore, a method in which an MBS transmitting apparatus provides allocation information for a zone and a zone flag regarding whether the last zone is allocated to a non-MBS region to an MBS receiving apparatus may be used.
According to this method, in a network including a zone #1, a zone #2, and a zone #3, the zone #1 and the zone #2 are allocated to an MBS region, and the zone #3 is allocated to a non-MBS region or an MBS region.
Accordingly, the MBS receiving apparatus served by the MBS transmitting apparatus belonging to the zone #1 and the zone #2 can recognize that the zone #1 and the zone #2 have been allocated to the MBS region based on zone allocation information and can recognize that the zone #3 has been allocated to the non-MBS region based on the zone flag.
However, the MBS receiving apparatus served by the MBS transmitting apparatus belonging to only the zone #1 cannot recognize whether the zone #2 has been allocated to the non-MBS region. Accordingly, the MBS transmitting apparatus belonging to only the zone #1 cannot allocate the zone #2 to the non-MBS region. Furthermore, the MBS receiving apparatus served by the MBS transmitting apparatus belonging to only the zone #2 cannot recognize whether the zone #1 has been allocated to the non-MBS region. Accordingly, the MBS transmitting apparatus belonging to only the zone #2 cannot allocate the zone #1 to the non-MBS region. Accordingly, waste of the bandwidth may not be avoided.
Meanwhile, Multi-Input Multi-Output (MIMO) technology may be classified into a Closed-Loop (CL) MIMO method and an Open-Loop (OL) MIMO method.
The CL MIMO method is technology that may use various channel information included in feedback information received from an MBS receiving apparatus when an MBS transmitting apparatus transmits data to the MBS receiving apparatus. According to the CL MIMO method, an MBS receiving apparatus estimates channel information for each channel through a plurality of antennas and transmits feedback information, including the various estimated channel information, to an MBS transmitting apparatus. The MBS transmitting apparatus applies the received feedback information to transmission data so that more accurate MIMO technical effects can be obtained. Accordingly, reliable and high-speed data transmission effects can be obtained.
The OL MIMO method is a method of transmitting data without using channel information included in feedback information received from an MBS receiving apparatus. The feedback information may not be sent in the OL MIMO method. Furthermore, although the feedback information is transmitted, an MBS transmitting apparatus may not use channel information included in a feedback message.
In general, in a communication system, the OL method may be applied to a channel environment for an MBS receiving apparatus that moves at high speed, and the CL method may be applied to a channel environment to an MBS receiving apparatus that moves at low speed. The OL method is applied to an MBS receiving apparatus moving at high speed because channels for the MBS receiving apparatus have a severe change and thus channel information included in feedback information is difficult to be reliable. On the other hand, the CL method can be applied to an MBS receiving apparatus moving at low speed because a channel environment for the MBS receiving apparatus has a relatively less change, various pieces of channel information included in feedback information is reliable, and communication apparatuses are less sensitive to delay.
Some subbands of a non-MBS region may be allocated to a region for MIMO. Accordingly, an MBS receiving apparatus needs to check a subband-based MIMO region for MIMO.
According to the method using zone allocation information and a zone flag, however, the MBS transmitting apparatus belonging to only the zone #1 cannot allocate subbands, belonging to the zone #2, to the MIMO region because it cannot allocate the zone #2 to the non-MBS region. Furthermore, the MBS transmitting apparatus belonging to only the zone #2 cannot allocate any subband, belonging to the zone #1, to a region for MIMO because it cannot allocate the zone #1 to a non-MBS region.